The Study On Close-coupled Catalyst And HC Trap For Automotive Exhaust Control

With the increasing serious pollution due to vehicle exhaust, the emission regulations become more and more strict world widely. In 2005, the Europeâ…¢regulation had been implemented in Beijing. To meet the Europeâ…¢regulation, there are many methods such as close-coupled catalyst, HC traps, electrically heated catalyst, chemically heated catalyst and secondary air injection etc. In this work, the techniques and materials used for the fabrication of close-coupled catalysts and HC traps were investigated.The wave-like structural metals are selected as the supports of close-coupled catalysts at first, and the coating properties of the metal with various surface treatment methods were studied. The results of the experiments demonstrated optimal pretreatment procedure of metal substrates was that the sample is first dipped in the 1.5 wt.% HCl solution at 100°C for 5 minutes, and then dipped in the 2.0 wt.% NaOH solution at the same temperature for 10 minutes, and finally calcined in air at 900°C for 5 hours.The ceramic fibers are also selected as the supports of closed-coupled catalysts. The influences of support composition and support pre-treatment procedures on the catalytic activity have been investigated. The investigation demonstrated that the alumina content of the ceramic fibers had large influence on the catalytic activity and the optimal pretreatment procedure of fiber substrates was the impregnation with 1wt % HCl solution for 30mins at room temperature.In order to get better catalysts, we prepared a series of catalysts with different contents of noble metal, cerium dioxide, and alumina. The catalytic activities of the catalysts were investigated for the methane and HC oxidization. The impregnation method is adopted to prepare the fiber-supported catalysts. Their catalytic performance was determined on the catalytic evaluation equipment, and the best performing catalyst was obtained. The best catalytic activities of the catalysts for the methane are 2wt%Pd/2wt%CeO₂/fiber and 2wt%Pd/2wt%Al₂O₃/fiber; the best...